1. Field of the Invention
The present invention relates to a lapping tape used for lapping of the surface of a magnetic head, magnetic disk or the like.
2. Description of the Related Art
A lapping tape which has a lapping layer formed on a flexible substrate is used for the precision finish processing of a magnetic head or surface finish processing of a magnetic recording medium. The lapping layer is formed by coating a paint for the formation of a lapping layer onto a flexible substrate, followed by drying. The paint for the formation of a lapping layer contains, in the kneaded or dispersed form, inorganic powders such as aluminum oxide, chromium oxide, silicon carbide, iron oxide, silicon nitride or diamond; an organic binder such as polyvinyl chloride resin, polyester resin or polyurethane resin; and other compounding agents.
As a conventionally known process for producing a lapping tape, there is a process as described in Japanese Patent Publication No. SHO 53-44714 which comprises heating an abrasive in the form of fine particles, mixing the resulting particles with a saturated polyester resin adhesive solution under stirring, filtering the resulting mixture through a filter, adding a hardener prior or subsequent to the filtration, coating the mixture onto the polyester film uniformly, drying and rolling up the film so obtained, and curing the resulting film. It is reported that the above preparation process brings about effects for preventing the fine abrasive particles from falling from the film surface. It is however difficult to say that the lapping tape so prepared has sufficient lapping ability.
In Japanese Patent Application Laid-Open No. HEI 7-276246, proposed is a lapping tape which has, on a flexible substrate, a lapping layer composed mainly of abrasive particles and a binder resin and wherein an extracted amount from the lapping layer by using tetrahydrofuran (THF) is 0.1 to 3.0 wt. % based on the lapping layer. It also includes the description that the amount of the solvent remaining in the coated layer is controlled to 0.1 to 40 mg/m.sup.2. An object of the lapping tape described in Japanese Patent Application Laid-Open No. HEI 7-276246, however, is to form a uniform chip streak on the surface of an electrophotosensitive drum for a copying machine, thereby bringing about a drastic improvement in the life of the photosensitive drum. The lapping tape is used exclusively for the above object and it does not seem to be suited to the lapping of a magnetic recording medium or magnetic head. In addition, in spite that the remaining amount of the solvent is indicated, it is only the indication of a numerical value and effects and advantages brought by the specification of the amount are not described specifically at all.
The present invention has been made in view of the foregoing situations. An object of the present invention is to provide a lapping tape which can prevent the occurrence of lapping scratches on the surface of the target to be lapped to the utmost, has a peeling-resistant of the lapping layer and has excellent lapping ability, upon lapping of the surface of a magnetic head or magnetic disk